There are prior art plants for making and packing respective articles, in particular in the form of rolls of toilet paper or paper towels, which are obtained from corresponding semi-finished products, in particular in the form of respective logs or reels of paper-based material, and which comprise an apparatus for making and packing the articles, located downstream according to the direction of feed of the material being processed, in particular comprising one or more lines for making and packing the articles, an apparatus, or section, in particular a rewinding machine for making the semi-finished product, which is located upstream according to the direction of feed of the material being processed, as well as means for accumulating or storing the semi-finished products, from which the making and packing apparatus, that is, the respective making and packing line, receives the semi-finished product and which, in turn, receives the semi-finished product from the apparatus for making a semi-finished product.
In the prior art plants the apparatus for making and packing rolls comprises at least one cutting machine upstream, which performs the transversal cutting of the rolls from elongate logs or reels, having a length which is substantially a multiple of the length of the single roll to be cut, and one or more packing machines downstream, which pack the rolls in special wrappers, made from a film of plastic material or paper, which contain a chosen number of the items, if necessary arranged in respective rows and, if necessary, positioned on several layers.
The packing machines provide for a certain number of types of packs of rolls, each having predetermined dimensions and comprising a predetermined number of rolls, arranged according to a predetermined configuration. Moreover, each type of pack also differs according to the type of roll (geometrical dimensions) and type of paper used for forming the rolls.
In the prior art plants, one or more cutting machines are normally used wih which respective roll packing machines are associated.
Machines from different manufacturers are generally used in the prior art plants for making and packing the rolls. This occurs, for example, due to the fact that the machines have been purchased at different times, or due to the fact that the machines have been chosen as a function of specific advantageous features which the machines possess.
In the plants according to the prior art and in particular in the plants using machines coming from various manufacturers, there is, however, a problem of coordinating operation between the rewinding machines, cutting machines, packing machines, bagging machines and/or palletizing machines, as well as of these with the conveyor belts connecting between the machines, which results in a decidedly poor actual efficiency of the plants, which does not allow sufficient use of the potential, in terms of high operating speeds, of the above-mentioned prior art machines.
In these traditional plants, the operational settings, in particular of the operating speeds, of the various cutting and packing machines and of the conveying apparatus, for example every time that it is necessary to adjust the operation to a change in size of the packs of rolls to be made—that is to say, to the number and arrangement of the articles which must be packed in a single pack—are made independently for each single machine, by the operators, who use respective keypads for entering the data in the respective PLCs or local control units of the above-mentioned machines.
This way of proceeding, which results in an adjustment of the plant which could be referred to as “manual”, is, however, quite unproductive. In effect, it is not easy for the operators to obtain a correct adjustment of the system, especially when it is necessary to control several size changes and the operators of the various machines have difficulty in communicating with each other. This also occurs due to the fact that the plants have very large dimensions and there is an objective difficulty in communicating, also as a result of the high noise level present in the plants, and in moving between the dense lines for conveying the articles.
Such a local adjustment of the operation of each machine of the plant usually leads to an incorrect operation of the plant.
To overcome these poor adjustments of the system in the prior art plants, use is made of normal automatic operation stopping controls, which are actuated by signals provided by maximum and minimum load optical sensors on the operational machines. In effect, it may occur that when the packing machines are fed with an excessive number of articles, a consequent automatic control signal is emitted for stopping the operation of the cutting machine upstream, whilst a corresponding signal for stopping the same packing machine is emitted when the machines are fed with an insufficient quantity of articles. Therefore, in the prior art plants, a fluctuating type of operation takes place, with work phases alternating with stoppages of the various machines of the plant. Thus, even in the presence of machines which are able to operate at high speeds, production outputs of the plant are achieved which are quite low, making futile the large financial investment for the purchase of these machines and, in any case, with a considerable waste of energy and excessive costs.
Moreover, this way of operating, which causes numerous stoppages of the cutting or forming machines upstream, as well as of the packing machines, also has adverse affects on the working life of the machines.
In effect, the components of the machines are subject to continuous accelerations and decelerations, to change them from the operating condition to the stopped condition, which produces stresses that, in the long term, causes faults to and wear of the main mechanical parts of the machines. The forming cutting machines comprise, for example, a large circular blade which, with a single movement in a plane transversal to the logs, or reels, simultaneously cuts several rolls, in particular a number of rolls equal to the number of logs which are fed to the cutting blade. Stoppages of the circular blade, due to emergency situations, can, over time, damage the movement mechanism of the blade, with significant repair costs and loss of production due to machine shut-down.
Moreover, in the traditional plants, the risk of overturning of the articles is high and the consequent stopping of the plant results in loss of production and, over time, the breakage and wear of the mechanical parts of the machines used. The number of overturnings which occur is influenced by the conveying speed of the articles and by the size of the rolls. Obviously, rolls which are short and have a large diameter have a higher risk of overturning.
Operating the cutting machine upstream at the maximum operating speed, as usually occurs, therefore increases the risk of overturning of the articles, at least with regard to certain types of products, such as the above-mentioned shorter rolls.
It should also be noted that, in the prior art plants, the rolls can be damaged, during transfer, by an excessively high conveying speed, especially a result of contact of the rolls with the conveyor guides.
Summing up, according to the traditional methods for regulating the flow of products in plants for toilet paper and paper towels there is an accelerated wear of the components of the plant, an excessive noise, an increase in the stresses and, therefore, risk of damage to the product, risk of overturning or poor positioning of the articles or products, and/or excessive energy consumption.
European patent EP1127791 describes a process for controlling the operation of a plant for the production of articles, in particular rolls of toilet paper, rolls of paper towels. As described in the above-mentioned patent document, a central processing unit takes data from the various machines of the plant and determines the respective maximum critical operating speed of the plant for the particular type of product.
According to the above-mentioned patent document, the operating speed of the plant is not greater than the critical speed.
Moreover, the above-mentioned patent document EP1127791 expressly states that, when a condition occurs in the plant that modifies the operation of the plant, the operation of the plant is reset as a function of the respective operating conditions of the other sections of the plant.
More specifically, the resetting procedure comprises, when the storage system which houses the logs has exceeded a number of pieces less than the predetermined level, in the event of an interruption to the feeding of articles to one of the machines or work units downstream, without reducing the operating speed of the cutting machine upstream, the operation of the plant downstream continues until the storage system is completely emptied.